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Noise-canceling headphones without the headphone

spectrum.ieee.org

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Re: Noise-canceling headphones without the headphone

#111

Post by ngneer »

coldtea wrote: post #87
ngneer wrote: post #5

Always great to see development in this domain. IWAENC and Silentium come to mind as the forefront. I hope one day the researchers will realize that they are trying to cancel the wrong source. Instead of cancelling noise external to the human, the real breakthrough will be to cancel the human voice. This will confer privacy and other benefits in areas of increased population density. I would prefer a smartphone to ha…

> I hope one day the researchers will realize that they are trying to cancel the wrong source. Instead of cancelling noise external to the human, the real breakthrough will be to cancel the human voice. Only few care for the latter and millions/billions care for cancellation of external sources. Besides, "cancelling the human voice" would just provide a false sense of security, as said voice would still need to be re…

That is what encryption is for. You only need to secure the voice until it can be encrypted.

Worth noting that the feeling of privacy is a lot about perception. People feel better if they know those they see around them cannot hear their private convo. That is why they speak softly and put their hands to their mouth talking in public places (the other part was to boost the signal, before the advent of differential microphones).

Don't get me wrong, I most definitely agree external cancellation is terrific, be it active or passive. In the passive realm people use traditional dampening materials, as well as MPPs (micro-perforated plates) in certain industrial applications.

Re: Noise-canceling headphones without the headphone

#112

Post by marcan_42 »

wegs wrote: post #105
marcan_42 wrote: post #96

Earlier quoted context omitted.

Active noise canceling earbuds already exist, and probably perform about as well as one can hope modulo small incremental improvements. I mean, the AirPods Pro are already damn impressive here. You could probably do better by cramming more and more technology closer to the actual ear /at the tip of the earbuds, perhaps? These things do cancel the low-mid end of voice frequencies quite well. I imagine with enough mini…

> But if you're going to draw a boundary and wrap it in a massive array of microphones... Aren't you better off just adding insulation material? :-) Well, let's do the math here. I can't find the data sheet for the weight of an electret microphone cartridge, but let's assume 4 grams. A thousand microphones -- assuming we want 100 the length of the airplane and 10 around -- is around 4 kilos. Add another 2 kilos for c…

Assuming you want to cancel frequencies up to 1kHz, you're going to need mics every 30cm at least for a useful sound field. For a 787 fuselage, that's about 60 around by 190, let's round that down to 10000 microphones. But of course, then you need electronics for them, and a way to carry the signals back to somewhere for processing. That's about 10 Gbps of data, fine, doable, but then you need to process it. Since you need to cancel separately per passenger, that's 2.4 million filters (10k mics * 242 passengers) to process. Nevermind that since this is a plane, there is a huge amount of overhead due to safety requirements.

This is all assuming this whole idea works, which it probably won't, because it's not just about the microphones on the fuselage but also how sound is transmitted inside the plane and other noise sources.

Re: Noise-canceling headphones without the headphone

#113

Post by mattmaroon »

sjg007 wrote: post #110
dghughes wrote: post #40

Earlier quoted context omitted.

Common rail diesels are very quiet compared to older style diesel engines. Some are so quiet you wouldn't even know it was a diesel. And with DEF you won't even smell the classic diesel exhaust smell. The loud smelling ones are due to modifications and probably also from "deleting" the DEF (which is illegal).

A large majority of these trucks get a delete installed. Numerous folks roll coal. In states without emissions control it’s a giant cluster.

I really doubt it’a a large majority.

Re: Noise-canceling headphones without the headphone

#114

Post by wegs »

marcan_42 wrote: post #112
wegs wrote: post #105

Earlier quoted context omitted.

> But if you're going to draw a boundary and wrap it in a massive array of microphones... Aren't you better off just adding insulation material? :-) Well, let's do the math here. I can't find the data sheet for the weight of an electret microphone cartridge, but let's assume 4 grams. A thousand microphones -- assuming we want 100 the length of the airplane and 10 around -- is around 4 kilos. Add another 2 kilos for c…

Assuming you want to cancel frequencies up to 1kHz, you're going to need mics every 30cm at least for a useful sound field. For a 787 fuselage, that's about 60 around by 190, let's round that down to 10000 microphones. But of course, then you need electronics for them, and a way to carry the signals back to somewhere for processing. That's about 10 Gbps of data, fine, doable, but then you need to process it. Since yo…

That sounds reasonable. Let's do the math your way in both directions:

1) Assuming system-level model

10,000 microphones * 8 kilosamples per second = 800 megasamples per second.

NVidia Tesla does 100 teraflops. I get about 125,000 FLOPS per sample. That feels adequate to me!

2) One filter per microphone per passenger. We need to divide by 250.

500 FLOPS per sample per passenger. That's more than enough for a very fancy IIR.

Of the two, I think #1 is more likely to work than #2, precisely because you want a coherent model. If you want to adjust your model for someone walking down the aisle (or any kind of system ID), that's a lot easier with 125,000 FLOPS per sample than 500 FLOPS per sample.

Re: Noise-canceling headphones without the headphone

#115

Post by wegs »

marcan_42 wrote: post #104
wegs wrote: post #101

Earlier quoted context omitted.

This comment is technically incorrect. Noise-cancelling headphones work the way OP described, and are limited to working in a cavity which is smaller than the wavelength. There are predictive noise cancelling systems too. These are commonly built into industrial equipment. You might, for example, have a fan or motor which spins at 5000 RPMs, and what do you know, it has a consistent noise profile on each of those rou…

Yes, as I said, this doesn't work in the general case when your noise source is uncorrelated and not predictable. If you have a predictable noise source then you've solved the time travel problem and you can cancel it any way you want as long as you can obtain feedback from the location of the user's ears. We're talking headrest ANC here (for use cases like consumer ANC headphones), not built-in noise reduction for i…

An airplane is an industrial system....

And in either case, the design of algorithms depends on much more on context than on whether it's "consumer" or "industrial." In this case, the context looks a lot more like industrial machinery.

Re: Noise-canceling headphones without the headphone

#116

Post by Solocomplex »

marcan_42 wrote: post #78

Edit: they cheated, this isn't ANC and will never work as ANC. See below. This sounds pretty fundamentally different from normal ANC. A common misconception is that ANC headphones "predict" the incoming noise and cancel it (and thus "they're good with constant noise but not sudden changes"). In reality they're just hybrid open-loop/closed-loop feedback systems. Specifically, the mic inside the cavity works with the s…

Some cars such as new Genesis models attempt this.

Re: Noise-canceling headphones without the headphone

#117

Post by thepostoffice »

jogundas wrote: post #77
thepostoffice wrote: post #51

I work in this area. There's a huge runway in front of us for both products and technology. 'Acoustic Holography' has worked for some time, commercial implementations have been few and far between, mostly because what's in the market is already selling boatloads without it. It'll come eventually, there are a few groups dedicated to it. A successful anchor in that space will allow companies to go deeper into applicati…

Sounds very interesting! Could you direct the interested to your favorite review article or another starting point?

An implementation or variation on this theme is surely the future of in-room audio:

https://en.m.wikipedia.org/wiki/Wave_field_synthesis

The math says, if implemented correctly, WFS is better than sitting in the sweetspot of any speakers. Also, there's no sweet spot with this technology.

Re: Noise-canceling headphones without the headphone

#118

Post by marcan_42 »

wegs wrote: post #114
marcan_42 wrote: post #112

Earlier quoted context omitted.

Assuming you want to cancel frequencies up to 1kHz, you're going to need mics every 30cm at least for a useful sound field. For a 787 fuselage, that's about 60 around by 190, let's round that down to 10000 microphones. But of course, then you need electronics for them, and a way to carry the signals back to somewhere for processing. That's about 10 Gbps of data, fine, doable, but then you need to process it. Since yo…

That sounds reasonable. Let's do the math your way in both directions: 1) Assuming system-level model 10,000 microphones * 8 kilosamples per second = 800 megasamples per second. NVidia Tesla does 100 teraflops. I get about 125,000 FLOPS per sample. That feels adequate to me! 2) One filter per microphone per passenger. We need to divide by 250. 500 FLOPS per sample per passenger. That's more than enough for a very fan…

Right, and now you've achieved the same noise cancelling performance... That off the shelf noise canceling headphones achieve (1 kHz) without putting 10000 microphones on the plane.

Again assuming this all works, which is a massive if.

Look, this isn't practical.

Re: Noise-canceling headphones without the headphone

#119

Post by taneq »

74d-fe6-2c6 wrote: post #97
JBiserkov wrote: post #3

>wearing active noise canceling headphones for extended periods of time can be uncomfortable and even cause injury Does anyone know what type(s) of injury is this referring to, how long is too long and how widespread/likely it is?

This is somewhat the pink elephant in the room when it comes to ANC. Last year lots of people complained about a simultaneaous reduction of ANC across several brands and models brought with firmware updates. One suspicion was that Bose, Sony, Apple have some info about possible damage from ANC and did this to avoid liability. I'm wearing ANC headphones up to 12 hours a day now for 5 years. I didn't experience any dam…

> Last year lots of people complained about a simultaneaous reduction of ANC across several brands and models brought with firmware updates.

Was this ever verified quantitatively? It sounds like the kind of thing that could easily be generated by group confirmation bias.

Re: Noise-canceling headphones without the headphone

#120

Post by originalvichy »

JBiserkov wrote: post #3

>wearing active noise canceling headphones for extended periods of time can be uncomfortable and even cause injury Does anyone know what type(s) of injury is this referring to, how long is too long and how widespread/likely it is?

I read a theory suggesting that eardrum fatigue is the reason. ANC does not hurt us even if it is loud. We are hearing a sound but not a ”real” one, but our eardrums still vibrate a lot. The thinking is that high level ANC is as fatigue inducing to eardrums as prolonged music listening. That’s why I nowadays recommend to friends to not use ANC on its own for too long daily.
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